The disclosure relates to a guide ring for a pump element of a hydraulic unit of a vehicle brake system for guiding a pump piston in a pump housing when the pump piston is displaced along its axis in the pump housing. The disclosure further relates to the use of such a guide ring in a hydraulic unit module for vehicle brake systems.
Hydraulic units are used in vehicle brake systems in order to provide a controlled brake pressure in associated brake circuits. For controlling the brake pressure the hydraulic unit comprises, among other things, at least one pump element, the pump piston of which is displaceable in a pump cylinder. In the area where brake fluid is admitted into the pump cylinder the pump piston is further guided in a pump housing, in which an eccentric drive for the pump piston is also located. A sealing arrangement, which is formed by a sealing ring, a support ring and a guide ring, is generally provided between the eccentric drive and the admission area. The sealing ring produces a largely fluid-tight seal between the admission area, representing an area exposed to slight pressure, and the eccentric drive, representing an area largely free of pressure. The support ring supports the sealing ring. The guide ring serves to guide the pump piston relative to the pump housing and thereby also relative to the pump cylinder. This guidance occurs at that end area of the pump piston where lateral forces are introduced to the pump piston by the eccentric drive. These lateral forces are absorbed by the guide ring. Moreover, the guide ring defines the overall space for the sealing ring and the support ring in an axial direction, in such a way that a sealing effect is achieved with a degree of play necessary for the reciprocating movement of the piston. A sealing arrangement of this type is disclosed by DE10 2006 036 442 A1, for example.
Hydraulic units of different capacities are needed for different types of vehicles and different functions in a vehicle. These various capacity classes are achieved by means of different pump elements and in particular here by different pump piston diameters. For this purpose the pump housings must be matched to the different pump piston diameters, making it necessary to produce a plurality of different pump housing variants.